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Unread 05-07-2012, 09:51
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Brandon Holley Brandon Holley is offline
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FRC #0125 (NU-TRONs, Team #11 Alumni (GO MORT))
Team Role: Engineer
 
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Re: CIM Motor Failure

Quote:
Originally Posted by Richard View Post
Brandon, I know you asked Al, but let me try. Al's post above indicated a possible in-situ diagnostic, namely motor current. If the motor is drawing more current while powering the same load (i.e., while the robot is performing the same operation), then it is either hot or starting to fail, or both. Allowing the motor to cool for a while, say an hour, and then repeating the same robot operation while observing the current will tell you whether the motor was merely hot, or failing.

Jaguars with CAN provide one method of monitoring in-situ motor current. WildStang published another method many seasons ago.
Thanks for the reply Richard.

The reason I ask, is we've had a weird issue regarding one of our drive sides all season.

We use 2 CIMs per side as most teams do, into a custom 2 speed gearbox. Even before ship date, we would monitor how warm the CIMs were getting during our testing. For some reason, one of the (4) CIMs always stayed cool to the touch. The partner motor to that one on the same drive side would become warmer than the 2 CIMs on the opposing drive side.

Thinking this motor just wasn't receiving power, we went through the debugging process, power the drive side with just 1 CIM and then alternating to make sure they both were "driving". We then switched the Victors that were powering them to ensure they were both "driving".

The motors always appeared to be functional, as in the robot would drive. However, during eliminations, or heavy testing, the robot would begin to pull slightly towards the "cold motor" side. We replaced the motors, and the issue has generally gone away.

I'm wondering if we were dealing with a CIM that was damaged from overuse/abuse or had a manufacturing defect.

-Brando
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